The present invention relates to a device for heating fuel prior to combustion in diesel or gasoline burning engines which are operated in extremely cold weather conditions. In recent years, considerable construction has been undertaken in such areas, as for example, the building of the Alaskan Pipeline. When operating motor vehicles under such conditions, the fuel, whether it be diesel or gasoline, becomes extremely cold and causes severe operational difficulties such as poor combustion resulting from the drop in the cetane rating of diesel fuel or octane rating of the gasoline and an increase in emitted pollutants caused by poor ignition. In addition, cylinder wash down often occurs from the raw or unburned fuel in the cylinders washing the lubrication off the cylinder walls and causing cylinder scoring. Unburned fuel also passes into the oil pan causing crank case dilution and fuel filters tend to freeze. The result of these occurrences is poor operational performance and frequent breakdown and repairs.
Several attempts have been made to devise a method for preheating the fuel prior to combustion to reduce the effects of extreme cold weather. Such attempts, however, have heretofore proved largely unsuccessful. Examples of devices previously developed are found in U.S. Pat. Nos. 3,253,647; 3,110,296; 1,267,185 and 1,168,111. While such devices may be of some benefit in cold weather operation, they generally require difficult adjustment which cannot be readily made by the vehicle operator. In addition, such devices generally employ coils which direct the fuel in a contained helical path through a reservoir of heated water. Fuel overheating can easily result if such devices are not properly adjusted which would cause the fuel to lose its lubricating and cooling effects resulting in sticking injectors and plunger scoring. In addition, gas separation can readily occur in the coils causing formation of air pockets in the upper portions of the coil resulting in vapor lock and engine failure. It would therefore be highly desirable to develop a device for heating fuel prior to combustion for use in both diesel and gasoline operated engines in extremely cold weather conditions which obviate the need for adjusting or regulating valves while avoiding overheating of the fuel and resulting in vapor lock. Such a device is disclosed herein.